1. Field of the Invention
This invention relates to electric shavers and, more particularly, to electric shavers adapted to erect low-lying facial hairs for cutting above the skin line.
2. Description of the Prior Art
Implements such as razors or electric shavers for cutting or shaving hair are well known in the prior art. Conventional shaving implements include a handle adapted to be manually held and means for mounting a blade on the handle. Most prior art shaving implements for cutting human facial hair are designed to cut hair close to the skin level and preferably beneath that level without nicking or cutting the skin. Toward this end, electric shavers have included a guard member or outer foil vibrated at an ultrasonic rate to substantially enhance the ability of facial hairs to enter guard apertures and be cut by a moving shear cutter to provide high cutting efficiency and close shaves. An example of such a shaving implement is disclosed in U.S. Pat. No. 3,756,105 entitled "Ultrasonic Electric Shaver," issued to Lewis Balamuth et al, on Sept. 4, 1973. Another electric dry shaver having a perforated freely rotatable outer foil or shear plate for following facial contours and improving operating efficiency is disclosed in U.S. Pat. No. 2,526,153 entitled "Multihead Dry Shaver," issued to Herbert E. Page on Oct. 17, 1950. However, prior art shaving implements designed to provide a close shave are unsuitable for use by people who suffer from a condition of pseudofolliculitis or inflammation of one or more hair follicles and pseudofollicles caused by ingrown hairs. It has been determined that pseudofolliculitis occurs in two principal forms of abnormal beard hair growth. First, beard hairs cut below the skin line may grow to penetrate the walls of their follicles in which they are growing and continue to grow along paths within the dermis or epidermis beneath the stratum corneum. Second, beard hairs growing along paths substantially parallel to the skin surface may penetrate folds or mounds of skin lying across their paths to form pseudofollicles which may become inflamed. It has been determined that both of these kinds of abnormal beard hair growth can be prevented by means of electric shaver and foil design according to the invention. Ingrown hairs of the first type are prevented by cutting all hairs above the skin line so as to negate the possibility of their penetrating the follicle wall. Ingrown hairs of the second type are prevented by cutting them before they attain sufficient length to span a furrow separating them from an adjacent fold of skin.
Shaving instruments such as prior art blade razors and electric shavers having a perforated stationary outer shaving foil are adapted to cut erect hairs at, and preferably below the skin line. This effect is obtained because the fluid-like nature of the fleshy layers beneath the skin permit razors or electric shavers to apply sufficient force to depress the skin around a beard hair causing the beard hair to protrude from the skin level by a length substantially equal to one or more hair diameters (the diameter of an adult beard hair is about 0.005 inch). In addition to depressing the skin around the hair, the fluid-like nature of the fleshy substrate permits the beard hair and immediately adjacent skin to protrude into the holes in a prior art electric shaver foil having a thickness generally less than 0.005 inch. It will be appreciated that a relatively thin electric shaver foil enables the cutter blades to shear or cut the hair substantially at the depressed skin level. When the force applied against the skin by a prior art razor or electric shaver is removed, it has been determined that beard hairs are often cut below the skin level or skin line. It has also been determined that hairs cut below the skin line tend to cause a pseudofolliculitis problem since such hairs sometimes become ingrown by penetrating the wall of the follicle and growing under the skin.
Prior art blade razors and electric shavers fail to exert sufficient lifting action on hairs growing substantially parallel to the skin surface. Hence, they remain uncut after repeated shaving, and grow to a length sufficient to penetrate and enter adjacent skin folds.
Obviously, a shaving implement designed to cut facial hair at or slightly above the skin line would probably prevent one cause of pseudofolliculitis. For example, shaving implements such as a prior art electric clipper with a stationary cutter normally held in contact with a user's beard are adapted to cut hair above the skin line. However, such a prior art electric clipper would not cut hairs emerging from the skin at a low angle. These low-lying hairs are a cause of pseudofolliculitis when they become ingrown by penetrating the stratum corneum across furrows and crevices in rough skin after about 2 days growth.
Accordingly, an electric shaving implement is arranged to cut hair, including low-lying facial hairs, so that all hairs are cut above the skin line and to a length selected to minimize future penetration of the cut hair into the skin.